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To: Andrew Cagney <ac131313@redhat.com>
cc: Richard.Earnshaw@arm.com, Kris Warkentin <kewarken@qnx.com>,
        gdb-patches@sources.redhat.com
Reply-To: Richard.Earnshaw@arm.com
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Subject: Re: [rfa?] Add frame_align(); Was: ARM stack alignment on hand 
 called functions
In-reply-to: Your message of "Thu, 28 Nov 2002 10:18:57 EST."
             <3DE633E1.7060900@redhat.com> 
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Date: Thu, 28 Nov 2002 08:33:00 -0000
From: Richard Earnshaw <rearnsha@arm.com>
X-SW-Source: 2002-11/txt/msg00715.txt.bz2

> >> +/* Ensure that the ARM's stack pointer has the correct alignment for a
> >> +   new frame.  */
> >> +static CORE_ADDR
> >> +arm_frame_align (struct gdbarch *gdbarch, CORE_ADDR addr)
> >> +{
> >> +  return (addr & -16);
> >> +}
> > 
> > 
> > Yuck, two's complement assumption.  I much prefer ~0xf in this case.
> > 
> > But why so much.  The maximum stack alignment you'll see on an ARM is 8 
> > bytes.
> 
> The function was lifted from the PPC code.  And, hey, what's a few extra 
> bytes between friends? :-)
> 
> Does (addr & 0x7) look better?
> 
> Andrew
> 
> 

As discussed elsewhere, the best solution (IMO) is

	 ~(CORE_ADDR)0x7

R.